The present invention relates to an overlay recording prevention device for an optical disc apparatus.
Since optical disc apparatuses can store a great quantity of data at a high recording density and read it out, they have been used in a variety of applications. According to the optical disc apparatus of this type, a pregroove formed in the optical disc is radiated with a low-level reproducing laser beam from an optical head. Reflected light from the optical disc is received by the optical head which then produces as a tracking signal a photoelectric signal corresponding to the reflected light. The optical head is then tracking-controlled in accordance with this tracking signal. The optical head emits a high-level recording laser beam onto the optical disc while the optical head is performing tracking of the pregroove, thereby forming recording pits in the pregroove of the optical disc. In this manner, when the optical disc is alternately radiated with the reproducing and recording laser beams, the optical head performs tracking of the pregroove and at the same time records data on the optical disc along the pregroove thereof.
However, when a strong impact or the like is imposed on the optical disc apparatus while data is being written in the optical disc, a tracking error occurs. This tracking error causes an erroneous shift of the recording laser beam spot onto an already-recorded track, thereby forming another recording pit thereon, resulting in overlay recording. In this case, the previously recorded data on the track is erased, which disables data retrieval and readout. Even if data can be retrieved, the readout data includes many errors.